Under investigation are: the function of a newly-discovered serum protein which binds heme and bilirubin, how the synthesis of the secretory proteins, albumin, hemopexin and transferrin is controlled, the details of ferrochelatase action which results in heme formation, and how the endogenous heme is transported to non-mitochondrial hepatic organelles. The significance of this work lies in improving the understanding and rationale for present therapy of states of iron overload, hemochromatosis, and porphyrin accumulation, porphyrias.